FAAC - Ford Amateur Astronomy Club

Binocular FAQ

Some Advice on Picking an Astronomical Binoculars

by Jay Reynolds Freeman (freeman@netcom.com)

The most important advice is to seek out a local astronomy club -- perhaps from the annual directory in Sky and Telescope or AstronomY. Go to some of their star parties to try out other peoples' telescopes, binoculars and other stuff. Sometimes people will be so eager to show you things that you can put off spending any money on equipment of your own for years and years.

The frequently-asked questions list for telescope purchasing, that appears on the usenet newsgroup, "sci.astro.amateur", has a good deal of information about binoculars. It includes a section on how to hold them steady. I recommend you wade through it and look for the sections you need.

Any binocular you happen to have lying around will provide much better viewing than the naked eye. So possibly you should not buy one at all, just mooch from friends or family for a while, till you know what you are doing.

Binoculars are intrinsically low-power instruments, that do not show a great deal of planetary detail. The moon will look wonderful, and you will be able to see the moons of Jupiter and the phases of Venus, but probably no other planetary stuff. Yet there are plenty of deep-sky objects well within the range of a small binocular -- I have seen all of the Messier objects with a 7x50 (but some were very difficult), and more besides. The Great Spiral Galaxy in Andromeda, the Orion Nebula, and the summertime Milky Way will be wonderful.

The "right" binocular for most people is about a 7x50 (that means it magnifies seven times and has front lenses 50 millimeters in diameter). The idea is to get as large front lenses as possible, so as to gather more light and see fainter objects, but with lenses much larger than 50 mm, or magnifications much greater than ten, the whole instrument starts getting too big and heavy to hold steady. Some people like more magnification than seven -- 10x50s are pretty common. I have a 10x70 which I like, but it weighs twice as much as a 7x50, and not everyone can hold it steady. It is also more expensive. If you are older than forty or fifty, the pupils of your eyes may not be large enough to take in all the light emerging from a 7x50 binocular; in that case a 10x50 might be best for you.

Some people pay as much as $1000 for a 7x50 binocular, but cheap and sleazy imports can be had new for as little as $50, and sometimes real bargains show up at garage sales and the like. If you are on a budget, do not worry if you have to buy the cheapest and sleaziest binocular you can find -- it will be lots better than the naked eye -- but expect your friends and fellow net-posters to be critical and condescending. Ignore us: We believe that having fancy gadgets makes us morally superior, we are dumb enough to think that more money always makes things better, and we are too cowardly ever to admit wasting money on something that wasn't worth the high price.

On the other hand, if you like high-tech gadgets, or if you are willing to pay a lot for the best binocular possible, and if you are certain you know exactly what you want, then go ahead and buy a more expensive binocular -- it will give noticeably better performance than a cheap one, but expect your friends and fellow net-posters to be critical and condescending. Ignore us: We believe that using inexpensive technology makes us morally superior, we are dumb enough to think that more money never makes things better, and we are too cowardly ever to admit that our needs and desires have outstripped our budgets.

Take care of your binocular. Things that will hurt it include heat (don't leave it in the sun, even in the case, especially inside a car), moisture, dust and dirt (do use the lens caps and case), vibration (don't toss it on the bed of your pickup for the drive up the mountain), and raccoons. Only the latter will take protection payments.

When you are about to buy a binocular, I recommend a few simple tests:

If it rattles when you shake it, you are about to make a mistake. Put it back and try another one. Don't laugh, a bad unit from even a reputable manufacturer may slip through quality control now and then, and who knows how many times the one in your hands has been dropped, and how far, in shipping and setting up for display.
Move everything that is supposed to move. Does anything feel loose and sloppy? Does anything feel like the only reason it is tight is that some unscrupulous manufacturer tightened it down too much, to cover up looseness and slop? These are all no-nos.
Can *you* get good images out of it? Take it to a door or window, preferably an open one, and focus it on something far away. If you had to take off glasses to use the binocular, are the images still clear? If you are using glasses, can you get your eyes close enough to the eyepieces to see the whole field? Is there any hint that the two sides are not perfectly parallel, so that only a chameleon can look through it without eyestrain? These are more no-nos.
Is it too heavy for *you* to hold steady? (Be sure you have read the FAQ section on how to do so.) Will you still feel that way after observing for an hour? Even when it's cold and you are tired?
Now a virtual test: Don't really do this, it's for experts only. Hold the binocular out at arm's length and drop it on the floor. I say again, don't really do it, just pretend that you are going to. If you have a virtual heart attack, or experience virtual financial ruin, perhaps you should consider a less expensive model. The theory here is that if you worry too much about loss or damage, you may end up babying the instrument so much you don't use it, in which case you are a collector of scientific instruments -- a fine and enjoyable hobby in its own right -- but not an astronomer.

Have fun, keep your dark adaptation, and remember -- raccoons like Oreos.